The present invention relates to separation and analysis of biomolecules, especially those of bodily fluids such as blood. It provides for moiety-specific sample extraction from a complex sample matrix in a flow through process. More particularly, the present invention relates to an integrated membrane for separation and preservation of classes of biomolecules, such as those in blood and other bodily fluids. These separated components are then available to be used for the diagnosis and testing for diseases and other medical conditions.